The storage system of grains in the so-called silo-bags is a technique that has gained great importance in recent times. As known, these are plastic bags of approximately 250 microns thick with different diameters and lengths, which are provided in the form of a tube. For example, a bag of 2.74 meters in diameter and 60 meters in length can contain 200 tons of corn.
During silage, an end of the bag is closed by the heat-sealing technique or simply by folding that end of the tube. The bag is opened as it fills and once the bag is complete, the opposite end is closed by any of the above-mentioned techniques.
A problem that has not been solved so far is the one derived from deterioration or rupture of the bottom or lower part of the silo-bag wall that comes in contact with the soil. This defect allows moisture to enter the silo-bag, causing the merchandise located in the lower part to be damaged or decomposed.
At present, the devices used for the extraction of the grains work according to one of the following combinations:                The bag is cut manually with different elements (i.e. knife) to later extract its contents by means of some mechanical or pneumatic device.        The device has cutting mechanisms that open the bag longitudinally as the machine advances removing the grains.        
A known mechanical discharger essentially includes a winding tube which is operatively associated with driving means of the rotary movement and which is mounted on support arms hinged to a wheeled frame containing elements for coupling and connecting to the power take-off of a towing vehicle. In the wall of the silo-bag, at one end, an upper longitudinal cut is made by which the product extractor device is inserted, and the winding tube pulls through that end by winding the wall of the silo-bag as the extraction of the product takes place.
In a machine of the preferred embodiment, the product extractor device is a continuous conveyor structure mounted on the machine frame, having a lower loading part substantially horizontally and transversely positioned within the bag-silo, and a part substantially oblique to the vertical, having a top discharge end in the cargo box of a loading vehicle.
From the information provided so far, prior art systems do not separate the spoiled grains, which contributes to lower the quality of the product being discharged and, in many cases, to render the load unusable.
Taking into account the current state of the art, a mechanical discharger of the type already explained is proposed, with the difference that two longitudinal lateral cuts are made in the wall of the silo-bag, being the wall divided into an upper part and a lower part. The end of the upper half portion is held and drawn by rotation by the winding tube which is articulately mounted on the frame support arms; in addition, a second winding tube has been incorporated, which is mounted underlying and parallel to the first winding tube, acting in synchronized form to hold the lower half portion of the silo-bag drawing it by rotation.
This improvement allows the substantially horizontal lower part of the extractor device to act only on the part of the product which is in good condition, while the lower layer of the spoiled product is drawn by the lower part of the bag wall as it is drawn by the lower winding tube and discarded through the open end of the bag.
Other features and advantages of the object of the present invention will be explained in the following description.
In these figures, the same reference signs indicate equal or corresponding parts.